Thanks all for the various info on picture and dado rails, etc; it's timely for me, as we're currently getting some redecorating done on our Edwardian house that's had all sorts ripped out, altered, partially (badly) reinstated, etc. and it's handy to know why various features were there.
I also remember picture rails, on the interwar council house I grew up in St. Leonards, as I was fascinated by the brassed picture hooks which were used for some of the larger pictures.
One of the alterations to the downstairs reception rooms in our current house is that the doors, which are in corners, have been re-hung (rather badly) so the hinges are in the corners rather than the knobs/latches...our decorator, who is Polish, said he was surprised when he first came to Britain that corner doors in older houses often opened in what seemed an awkward way, and was told that it was to give the occupants of the room warning that someone was coming in so they would not be seen doing, well...whatever it was they were up to!
Don't know whether this explanation is true or not, but it sort of fits, I suppose!
Simon.